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UBC Theses and Dissertations

Effect of isometric training with short or long rest periods on Achilles tendon morphology : an ultrasound tissue characterization study Alketbi, Thuraya


Achilles tendon (AT) is the strongest tendon in the body. One of the major causes of AT pathology, chronic tendinopathy, is frequently due to excessive loading. Despite the risk of overuse injury, exercise training with appropriate mechanical loading parameters has been found to trigger an adaptation response in the AT. However, the influence of some loading parameters, such as the duration of rest periods between exercise repetitions, remains unknown. Therefore, the aim of this study was to examine the effect of 10s rest insertion during isometric resistance training (Long rest training; LRT) on the morphological properties of human AT, compared with same training intensity and volume but with 3s rest insertion (short rest training; SRT). I hypothesized that ATs exposed to LRT would demonstrate increased tendon collagen organization and tendon cross-sectional area (CSA) compared with baseline, but that SRT would not demonstrate any change in either variable. To test my hypothesis, we recruited healthy adults, and randomly allocated one leg to LRT and the other to SRT. The exercise protocol consisted of 5 sets of 10 isometric calf presses at 90% of maximum voluntary contraction, three times a week over a 12-weeks training period. Tendon collagen organization (proportion of type I echoes) and CSA were measured by ultrasound tissue characterization before and after the 12-weeks period. The primary outcome was the proportion of type I echoes. In contrast to our hypothesis, neither LRT nor SRT induced an improvement in collagen organization or tendon CSA. However, tendons exposed to SRT demonstrated a reduction in the proportion of type I echoes following exercise from 0.66 (95% CI= 0.60 to 0.70) to 0.55 (95% CI=0.49 to 0.60), (p < 0.05), whereas tendons that were exposed to LRT didn’t demonstrate any reduction in the proportion of type I echoes from baseline (0.60, 95% CI= 0.56 to 0.65) to post-intervention (0.62, 95% CI= 0.57 to 0.67), (p = 0.58). Neither type of exercise had a measurable effect on the AT CSA. Further research is needed to examine the biological changes and mechanical effects that influence tendon morphological change associated with different exercise parameters.

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